An IEEE (Institute of Electrical and Electronics Engineers) 802.16 standards provide techniques and protocols to support a broadband wireless access. Standardization proceeded starting from 1999 and IEEE 802.16-2001 was approved in 2001. It is based on a single carrier physical layer called ‘WirelessMAN-SC’. Later, besides the ‘WirelessMAN-SC’, ‘WirelessMAN-OFDM’ and ‘WirelessMAN-OFDMA’ were added to the physical layer in IEEE 802.16a standards approved in 2003. After the IEEE 802.16a standards were completed, revised IEEE 802.16-2004 standards were approved in 2004. IEEE 802.16-2004/Cor1 was completed in the form of ‘corrigendum’ in 2005 in order to resolve and correct bugs and errors of the IEEE 802.16-2004 standards.
One of systems considered in the next generation is an OFDM (Orthogonal Frequency Division Multiplexing) system that can attenuate an inter-symbol interference effect with a low complexity. The OFDM converts serially inputted data symbols into the N number of parallel data symbols, carries them in the N number of separated subcarriers, and transmits the same. The subcarriers maintain orthogonality in a frequency domain. The respective orthogonal channels experience mutually independent frequency selective fading, and the intervals of transmitted symbols are lengthened to minimize the inter-symbol interference. OFDMA refers to a multi-access scheme accomplishing multiple accesses by independently providing portions of available subcarriers to each user in a system using the OFDM as a modulation scheme. The OFDMA provides frequency resources called subcarriers to each user, and in general, the respective frequency resources are independently provided to multiple users so as not to overlap with each other. That is, resultantly, frequency resources are mutually exclusively allocated to the users.
In the OFDMA system, frequency diversity can be obtained for multiple users through frequency selective scheduling, and subcarriers can be allocated in various forms according to permutation with respect to the subcarriers. The efficiency of a space domain can be enhanced according to a space multiplexing scheme using multiple antennas. In order to support such various schemes, a control signal should be necessarily transmitted between a UE (user equipment (UE)) and a base station. In particular, as an HARQ (Hybrid-Automatic Repeat Request) scheme obtained by combining an FEC (Forward Error Correction) scheme and an ARQ scheme is used as an error compensation scheme to ensure reliability of communication, control signals such as a response to a data transmission, re-transmission request, or the like, are frequently transmitted. With the limited radio resources, the more the control signals are transmitted, the more radio resources that can be allocated for data transmission are reduced.
Thus, a method for effectively using limited radio resources by reducing the amount of radio resources allocated for the control signals is required.